This invention relates to a composite material useful as an interior material for automobiles and to a method of preparing same.
As an interior material for automobiles, a composite material having a surface skin layer and a polypropylene foam layer is utilized. One known method for preparing such a composite material includes bonding the skin layer to the foam layer with an adhesive. This method is disadvantageous from the standpoint of economy because the adhesive must be used and because the method is complicated. Another known method includes expansion molding expanded particles in a mold together with the skin layer. The composite material obtained by this process has a problem because of lack of surface softness and of formation of depressions in the skin layer corresponding to those in the foam layer.
JP-A-H6-891 discloses a method in which an extruded laminate of a polypropylene skin layer with a cushioning layer of non-crosslinked polypropylene is placed in a mold and expanded polypropylene resin particles are molded in the mold together with the laminate. This method has a problem because the composite material thus obtained has low adhesion between the laminate and the molded foamed layer of the expanded polypropylene resin. When the process conditions are changed so as to obtain satisfactory adhesion, then the cushioning layer is depressed.